Distillation system



l. LEA 2,398,836

s sheets-smet 1 April 23, 1946. H

DISTILLATION SYSTEM Filed Feb.. 13, 1945 D 6. 4 9 1 ,3., 2 r P. A

3 Sheets-Sheet 2 Filed Feb.V 13, 1945 W//N///f/ M l 12. L e cz Y' @L l.LEA

DISTILLATION SYSTEM` April z3, 1946.

Filed Feb.. 15,1945 5 sheets-sheet 3 TEMPERArl/RE (DEG. F.)

O O ol,

PERCENTGE OFSEA WATER E MAPORAMBZE BEFORE REMAIN/NG BR/NES 5A TURA TEDAs 7'0 @c1504- 20 25 30 Inventar Patented Apr. 23, 1946 DISTI'LLATIONSYSTEM Henry I. Lea, Santa Monica, Calif.; Grace Joel4 Leaadministratrix oi said Henry LLea, de-

t ceased -'Application' February 13, 1943, serial No. 475,785

14 Claims.

The general type of system and apparatus for fluid heating anddistillation to which this present invention relates is shown in severalparticular and illustrative forms in my previous patents, No..1,845,159, Feb. 16, 1932; 1,889,254, November 29, 1932; 1,971,492,August 28, 1934; 1,990,831, `February 12, 1935. The unitary distillationap-` paratus of those patents is characterized generally by anarrangement 4of an evaporator within a vapor space or chamber which inturn is within a condenser through which the cool raw fluid isintroduced. The general arrangement promotes a high thermal operatingefficiency by retaining and recycling within the system a largeproportion of the heat required for vaporization, And with therelatively cool condenser at the outside,

the `heat lossesA by radiation and conduction are small.

The present invention has as its objectives several improvements in boththe apparatus and method of that type of distillation or fluid heatingsystem, all of which will be made most clear in the following detaileddescriptions of preferred structuresand operations. I may howeverment-ion preliminarily that, although my former specific embodiments anddesigns, built and tested,

Vhave attained high thermal efficiency and were capable of longoperating life, the structures have y been relatively expensive tomanufacture. One of the purposes of the present improvements is toprovide a form of unitary apparatus whichis simple and of low cost andstill at the same time is capable of maintaining the desired higheiliciency through a long operating life, Although my present heatingand distilling system is capable of many diverse uses it has beenparticularly designed for a certain' type 0f use which I will explain.Generally Speaking, lthe system and apparatus may be used for heating ordistilling any type of liquid, for various purposes,

and operated under a wide range of temperatures and pressures preciselymaintained. The apparatus may be used as a simple liquid heater, or itmay be used for the liberation of entrained orv dissolvedvgases fromliquid, such as the liberation of ammonia gas from its liquor orsulphurous gases from water; It may be used either to distill all or afraction of its feed liquid. under any properly chosen conditions oftemperature and pressure. However, one of its most useful functions isthe distillation at high thermal efliciency,

of a fraction of the feed liquid, and'at temperatures and pressures(which may be sub-atmos- Sea thing that issoluble in water; -it holdseach of these substances within a specific temperature range; it losesthem all on freezing.; with rising temperature, to a definite point thesolubility for each of them increases, then decreases, following areversed solubility curve. Depending on the pressure to which it isexposed, water can be evaporated at temperatures as low as freezing:therefore it is possible to evaporate water at temperatures below thoseat which it begins to lose its ability to hold in solution those limeand magi nesia compounds from whichfpractically all scale problemsarise. It is possible to evaporate a considerable percentage of seawater while leaving in l5 the brine, still in solution and ready to becarriedv off with the brine as waste, all of thescaleforming matter ofthe original volume of sea water. y

The distillation system of my present invention is capable of distillingsuch liquors as sea water in the manner just indicated, maintaining highthermal eiliciency in a simple inexpensive apparatus. The followingdetailed description of illustrative preferred forms of apparatus, andits illustrative application to such .liquids as sea water, will makethe invention clear.

In the accompanying drawings:

Fig, 1 is a central vertical section of one illustrative preferred formof still apparatus;

Fig. `2 is an elevational diagram of the still,v

with parts broken away in section, and illustrating the circulationsystem;

Fig. 3 is a fragmentary cross section yon line 3-3 of Fig. 1:

Fig. 4 isa vertical central section of an illustrative variant form ofstill apparatus; and

Figs. 5, 6 and *l are diagrams illustrative of my method ofdistillation.

Referring first to Figs. 1 and 3 the still apparatus is illustrated asbeing enclosed within an outer shell I0, which may be exteriorly heatinsulated as at Il, if desirable. Inside shell i0, and preferablylocated close to the shell wall, is a. condenser I2 preferably in theform 0f espiral tube connected at its lower end to the raw liquid intakeI3, and connected at its upper end toa vertically extending tube ilwhich conveys the then heated raw liquid into a head chamber" i5 whichis located at the lower end of the apparse. y tus immediately beneaththe tube sheet I8 ofthe vaporlzer.

The particular -form of condenser here shown is preferred, butillustrativ'ely typical. Any other form may be used which is suitablefor arrangelment in an annularspace close to or in association with` theexternal shell I0. The first mentioned one of my previous patents showsother typical forms which may be used.

Figs. 1 and 3 show a vaporizing heater designed to receive its heatinput from steam or 'i0 other hot vapor or liquid, although, as will ap.

v at its outlet porized. The lower ends of tubes 22 communicate withhead chamber which is formed within a cylindric shell 23 projectingupfrom the bottom plate 24 which closes the lower end of the largeexterior shell l0. Member 23 and end plate 24 may be formed in anysuitable manner; but may economically be formed of sheet or plate orcast metal, integrally, or welded together, and

plate 24 may be welded to the lower edge of shell I0. The lower end ofhead chamber l5 is closed by removable plate 25, through which projectsa pipe 26 which leads from the lower end of the evaporator` for carryingofi the cooled or condensed heating fluid. The heating iiuid, steam inthis case, enters the upper end of the evaporator through pipe 21 whichleads through a removable cover plate 28 mounted on the upper closureplate 29 which closes the upper end of shell I0. Closure plate 29 mayalso be welded to shell l0.

ILower tube sheet I6 is shown as of larger diameter than 'the evaporatorshell 20, extending annularly outside the diameter-,of the lower end ofthe evaporator to form a support for an upwardlylcylindric baille v30whose upper edge is located closely under the upper closure plate 29.The extended tube sheet i6 thus also forms the bottom for an annularchamber which is enclosed within baille 30. From this annular chamberthe 'unvaporized residue liquid is removed through discharge pipe 3|which lower closure plate 24.

A second baiile 32, inside of baille 3|) and spaced from that baille andfrom evaporator shell 20, depends from upper closure plate 29 and hasits lower edge located at a substantial distance above tube sheet I6,that location being for a purpose which will appear.

For certain purposes, which will appear, an insulating shell 33 may behung from flange 2|a of upper tube sheet 2|, spaced from but closelysurrounding evaporator shell 20, and with its lower edge close to butslightly spaced from from flange. |6a of lower tube sheet I6.

.A distillate discharge pipe 35 leads from the lower end of the annularcondensing chamber formed between outer shell I0 and outer baille 30.This discharge pipe is fitted into lower closure plate 24, convenientlyin such a relative Dosition as shown in Fig. 1, and leads through a trap36. The residue discharge pipe 3| also preferably leads through a trap31, as shown diagrammatically in Fig. 2. Trap 31 communicates end with a-pipe 38 which forms the Ilnal discharge pipe for the residue and whichprojects down through v has an upward extension 38a which projectsthrough bottom closure plater 24 into the an' nular condensation chamberwhich is formed between outer shell I0 and outer baille 30. The up- Deropen end of pipe 38a is hooded to prevent entrance of falling liquid andprojects to a level safely above the depth of distillate which may standabove the bottom o'f the shell. Y

As Iindicated diagrammatically in Fig. 2, the

live steam feed pipe 21 may be equipped with a control valve 40 whichmay be automatically controlled, through the medium of the mechanismdiagrammatically indicated at 4|, by a thermometer bulb 42 which is'hungfrom upper closure plate 28 in a position just above the upper end ofthe evaporator, where the instrument will be responsive to thetemperature of the vapors issuing from the evaporator tubes..

As has been indicated, for certain purposes such as the distillation'ofsea water it is desirable to operate the apparatus under sub-atmosphericpressures. Systems for so operating a still are of 'course well known inthe art, and any suitable system for low pressure operation may beadopted. By way of illustration for the purpose I show in Fig. 2 apositive feed pump 4| connected with feed pipe I3; andpositive vacuumpumps 42 and 43 connected respectively to residue outlet 38 anddistillate outlet trap 36. These pumps may be of any positive type, suchas a rotary blade type, and driven by any suitable controllable means.The pressures at which the still is operated may be set and maintainedby setting and maintaining the effective evaporating temperature of theheater and the relative rates of raw liquid input and residue anddistillate withthe other tubes and pipes within and the tube sheets ofMuntz drawal; and, if desired those rates of input and withdrawal may beautomatically regulated andl controlled by automatic regulation andcontrol of the volumetric speeds of operation of the several pumps.Means for so setting and regulating the speed of pumps are well known inthe art and need not be illustrated here.

Gauge glasses 34 and 39 may be used to indicate, respectively, thelevels of the residue brine and of the distillate. `Because of equalizedpressures in the apparatus these glasses will show true levels. Forconvenience of observation they may be located close together; they areshown in the diagram of Fig. 2 at opposite sides of the -unit merely forconvenience of illustration. By adiusting the speeds of the two vacuumpumps, with the raw water feed pump delivering raw liquid at a fixedrate, and with temperature conditions within the unit stabilized, fixedlevels in the two gauge glasses can be maintained and correct operationof the unit assured. Automatic level controls of known types may beapplied to the gauge glasses if desired. A vacuum gauge, as indicated at44, may be used; and automatic controls of known types may be actuatedby the gauge to maintain the desired operating pressure. l

Any materials suitable may be utilized in the still structure, butmaterials of certain types are preferable. The vaporizing tubes 22 arebest made of a material such as Admirality metal, metal. The outer shellof the heater may be of gun metal, and the bailles 3|) and 32, theshielding tube 33,-and the condenser coil, of tinned copper. The top andbottom plates, the distributing chamber I5, and the structure, and thestuffing boxes, may best be made of gun metal. It is preferred, as faras is practicable, to secure and connect all of the various elements bywelding, brazing, or the like.

Typical operation of .the apparatus which has now been described, may beas follows. Live steam for the boiler, or exhaust steam, automaticallycontrolled as to volume, pressure and temperature, is introduced throughpipe 21 to the aaoaeae passing out through discharge pipe 26 may flowinto a direct return trap and so be forced back, automatically into theboiler feed line. Operating in that manner no water is lost from theboiler feed supply, and the boilers are called upon only to provide thelatent heat given up by the live steam while passing through the still.

The raw sea water enters the lower end of condenser coil I2, controlledas to volume and pressure by :the operation of pump 4I. That watertravels spirally upwardly to the upper end of con( .iser coil I2 andthen down through tube M to enter the distributingghead chamber l5 andthe lower ends of evaporator tubes 22. Passing up through evaporatortubes 22, the water is heated from the steam surrounding the tubes inthe evaporator, until the temperature of the water and of the generatedvapor reaches the desired point, which is controlled by the automatictemperature' control described. This temperature is xed and maintainedpreferably just below the temperature at which the residue water beginsto lose its capacity for holding in solution thosev solids which wouldotherwise precipitate and form scale. Rapid evaporation of the water atthat relatively low temperature is facilitated by maintaining a partialvacuum by means o operation of the discharge pumps.

Having reached the top of the evaporating heater, the mixed water andvapor, together with occluded or dissolved gases which have been freed,overilows the top of the evaporator and flows down through the annularspace around the evaporator and inside inner baille 32. At the lower endof baffle 32 where the stream of fluids reverses its direction of llowto flow upwardly outside of baffle 32, a separation occurs. VThe annularspace between baille 32 and heater shell 2n (or the insulating shell 33)is made narrower than the annular space between inner baffle 32 andouter baille 30. The velocity ofV downward flow of mixed liquid andgaseous fluids to the lower edge of inner baille 32 is consequentlycomparatively high. Upon reaching that lower edge, the unvaporizedresidue water, carrying all of the dissolved solids and at least a partof the entrained and dissolved gases, tends to dow on downwardly, due toits weight and mass, and is projected onto bottom tube sheet I6 at thelower end of the annular space between evaporator shell 20 and outerbaille 30.

`The water vapor, still uncondensed, together with some of the entrainedgases, then flows comparatively slowly upwardly through the largerannular space between inner baiile 32 and outer baille 30. This slowupward flow has no great tendency to carry entrained liquid particlesalong with it; and any such entrained unvaporized liquid has theopportunity of owing back down through the annular space to join theaccumulation of residue liquid which ilows out through residue pipe 3l.Thus, nothing but comparatively dry vapor and some fixed gasesreach thetop of outer baille 30 to iiow over the upper edge into the upper end ofthe annular condensation passage between outer baffle 30 and is operatedto draw off the condensate and maintain the desired low pressure..Whether or not a body of condensate liquid is maintained to some depthin the bottom of the apparatus, above lower plate 34, depends upon theconditions at which operating equilibrium of the system is attained.

In normal continued operation oi the system the amount of raw waterintroduced in unit time is always sulcient to take up all of the latentheat of vaporization of that fraction' of the liquid which has beenevaporated. The vapors are completely condensed before reaching thelower end of the condensing passage. Consequently, in the lower -part ofthe annular condensin-g passage there can only be present the condensateand the air or other 'gas' which has been released from entrainment orsolution and which has reached the outer condensing zone. I provide thestand pipe 38a for the purpose of removing such fixed gases from thesystem and preventing their accumulation, the open upper end of thisstandpipg being somewhat above lower plate 24, aspreviously stated.Standplpe 38a communicates directly with the residue outlet p 38 whichleads to vacuum pump 42. Vacuum pump 42 thus takes -both air throughstandpipe 38a and the residue liquid through trap 3l, and is operated atsuch volumetric speed as will maintain the desired low pressure in thesystem. A certain portion of the released fixed gases may be drawn outthrough trap 3T along with the residue'liquid. All of such releasedgases would be so drawn out if the special gas pipe 38a were not used solong as a body of residue liquid does not stand over lower closure plate2d. The provision of the special standpipe 38a insures withdrawal of thegases, and prevention of their accumulation, if a body of residue liquidstands over the lower plate in normal equilibrium conditions ofoperation.

'Ihe purpose of shielding tube 33, around the evaporator shell 20, is toprevent local overheating of the unvaporized water passing down over theevaporator shell. It will -be understood that as the water ilowsdownwardly over the evaporator shell and inside the inner bale tube 32,

it continues to be heated and, `at least to somey extent, vaporized byheat from the steam in the evaporator. 'Ihe major evaporation haspreviously taken place while the water has passed up through theevaporator tubes 22. The exterior surface of evaporator 'shell 2D is solarge that, at ordinary velocities of ow through the apparatus, the flowover the outer surface of the heater shell may be more or less irregularand without assurance of maintaining a continuous film of water over thewhole of the shell surface. And in installations where the still cannotbe maintained in vertical position, as on shipboard, the malntenance ofa continuous unbroken film of liquid over the shell is substantiallyimpossible.

With live steam at about 240 or so inside the shell, and` with areas ofthe shell alternately flooded and dry. scale formation on the shellsurface is almost a certainty. The thin copper shielding tube 33 has thefunction of enclosing 4a substantially dead air space immediatelyadjacent evaporator shell 20 to act as an insulator or 'the' wateriiows, and thus prevents the formation -of scale A The shielding tube 33 is preferably not s,tzfuctur'ally joined at its lower end -to thelofwer tube sheet I6, but hangs suspended from its upper end, to avoidstresses and distortions due to differential expansions andcontractions.

Although I may prefer to provide such a shielding tube, any suitableinsulating jacket or layer around the evaporator shell will sulce. Forinstance. a uniform layer of scale deposited upon the shell will performthe same function; and that layer of scale may be provided by simplyoperating the still without a shielding tube 33 until a uniform layer ofscale has been deposited over the Whole shell surface to a thicknesswhich provides a suilicient retardation of heat iiow to prevent anyfurther localized overheating of the liquid.

With any such insulation for the evaporator shell, the downwardly owingvolume of liquid still receives some heat from the live steam in theevaporator; but the major portion of the Vaporizing heat is transferredto the liquid while it is passing at relatively high velocity, andturbulently, through the relatively small evaporating tubes 22 where therate of heat transfer is highest. A

Although the system is capable of lbeing used under wide variations ofoperating conditions, a

statement of one set of conditions will be illustrative of the operativeeciency of the system as applied, for instance, speciiically to seawater. As a basis for this description, I may state that Figs. l and 3of the drawings are to scale, and that the apparatus has been designedto produce around one U. S. 'gallon 'of pure distilled water per minutefrom sea water, when the 4apparatus is of such size that. the diameterof outer shell i (to fix the scale) is approximately 25 inches. For fullcapacity production at highest thermal emciency an apparatus of thatsize requires the heat which is supplied by live `steam delivered to theunit under a pressure of lbs. -per sq. in. and equivalent temperature of240 F.,and at the rate of 11.3 lbs. weight of steam per minute. Thevolume of live steam needed, and also of the rawwater input, aredependent of course upon the percentage of the rawwater which it isdesired to evaporate. The unit has a Wide range of heating or distillingcapacity, dependin-g on the ratio of heat input to raw water supply, andupon the temperature of operation; it can act merely as a heater of rawwater, or it can distill off any desired percentage oi raw water, up tothe point at which the resulting brine becomes saturated. it can ofcourse distill ofi' a stillhigher percentage even though there be anaccompanying precipitation. But the optimum conditions oi operation arethose which result in the highest thermal eihciency, and usingevaporation temperatures which are around the temperature of maximumsolubility of the solutes in the water.

'Ihe highest thermal emciency is reached when the volume of the incomingraw water is such that its heat capacity in rising from its normaltemperature to yaporizing temperature (at the corresponding operatingpressure) is Just suflicient to take up the latent heat of vaporizatonofthe fraction of water which has been vaporized and the availablesensible heat of its condensate. For instance, with rawwater at around60 F., and operating at normal pressure and temperature of evaporation,the condition of highest thermal eiliciency allows the evaporation ofone pound of water out of each '7.14 pounds, or about 1,4%, of raw waterintroduced. This evaporation fraction varies oi course ior diKerascasseent liquids, and varies with the initial liquid temperature.v andalsowith dierent evaporating temperatures; but the fraction lust stated canbe .taken as typical for water. Operating at this condition of highestthermal efliciency. a liquid may be, run through the operation offractional evaporation either once or successively a number of times,either through the same distillation unit or through a plurality ofmulti-stage units, until the solids in the residue solution approach. orreach the saturation point. The optimum temperature at which theevaporation is carried on (governed by the controlled pressure at whichevaporation takes place) can be best understood from the diagrams ofFigs. 5, 6` and 'l and the following explanation, again using thedistillation of sea Water as a typical example.

In analysis, ordinary sea water is nearly uniform throughout the world;its total salts range from about 3.7% in tropical regions to about 3.5%in frigid regions. A typical analysis of sea water (this taken from theEnglish channel) is as follows:

Per cent by weight Sodium chloride/(NaCl) 2. 805 Magnesium chloride(MgCla) .366 Potassium chloride (KCl) 076 Magnesium sulphate (MgSO4-).23

Calcium sulphate (CaSAOi) f.. .14 Calcium carbonate (CaCOa) 003 Calciumbromide (CaBr) 003 3. 624 Traces of a great many other salts---" 003 3.627 Ordinary water l i 96. 373

Sea -water 100.000

The above analysis shows relative weights of these salts in sea water tobe as follows:

Salts such as sodium chloride have such a large solubility in water, andincreasing solubilities with increasing temperatures, so that it isimpossible to precipitate them at any temperature which is herecontemplated unless the fraction distilled is carried far beyond anyfraction which I contemplate.` For instance, approximately 90% of seawater can be distilled oi before the residue brine is saturated withsodium chloride. Generally speaking all sea water salts which show aconsistent rise in solubility with increase in temperature withinthetemperature ranges contemplated here may bel dismissed from furtherconsideration. 4 i

The problem iswith the scale forming group, all ofwhich are believed toyshow reversed solubility characteristlcs-increasing solubility withincrease oi. temperature up to a given point, and

l then decreasing solubility with further temperature increase. Calciumsulphate (gypsum) is typical of the scale forming group; its solubilityasaasae characteristics are shown in the diagram of Fig. 5. .'Of themain scale forming substances, the carbonates and sulphates of magnesiumand calcium, only the sulphate of calcium is present in sea water in aconcentration at all approaching saturation. If sea water can bedistilled without precipitation of that sulphate, no precipitation ofany substance occurs.

'I'he curve of Fig. 5 shows the reversed solubility characteristics ofcalcium sulphate. Highest solubility lies at about 104 F. where about2110 parts per million are soluble. At 212 F. only about 1700 parts aresoluble; at 155 F. for instance, and also at 55 F., approximately 1950parts are soluble; and at 143 F. and 62 F., approximately 2000 parts.

As shown by the first table above, sea Water carries 1400 parts permillion of calcium sulphate. For the moment disregarding temperaturesand solubilities, the effect of removing various percentages of waterand leaving the sulphate in the residue brine is shown in the followingtable.

Grams of calcium sulphate per million grams of the Percent of sea waterevaporated v remaining brine If 14% of sea water is evaporated, thereare 1628 parts of the sulphate per million left in the residue brine.

Since solubility of the sulphate varies with temperature, the percentageof raw water that can be evaporated before the brine becomes a.saturated solution also varies. The curve in the diagram of Fig. 6 showsthe limiting percentages at different temperatures. The curve shows thatat 212 F., only 1'71/2%. can be evaporated; but at 155 F., or at 55 F.,approximately 28% can be removed; while at 104 F., approximately 33/2%can. be removed. If 14% is to be removed, the margin of safetythroughout the range from 55 to 1559 F. is approximately 14% or more;but at temperatures between 155 and 212 F. the' margin falls withincreasing temperature until it is only 31/2 at the latter temperature.At somewhat higher temperature the brine would be saturated.

The curve in Fig. 7 shows the percentage ofsaturation oi the brine atthe same range of temperatures when 14% of the original raw water Itthus appears that, to operate under optimum conditions of thermaleiilci'en'cy (assumed here to involve evaporation of 14%) and at thesame time to avoid possibility of scale deposit one at least mustoperate in the temperature range in which the residue brine does notbecome supersaturated. For calcium sulphate in sea water, that rangeruns up to approximately 228 F. To allow for local overheating, thetemperature range should allow a margin of safety, such as is allowedin. the range from approximately 55 to 155 F. or thereabouts. Withinsuch a range of safe margin I choose preferably to operate at or nearVthe higher limit, say around 155 F., as the productive capacity of agiven sized unit is apparently greater at a higher than at a lowertemperature. v l

Thus, the choice of evaporating temperature range in which the residuedoes not become supersaturated; preferably within a more limited range lwithin which the brine lacks saturation by a safe is evaporated. When14% is removed there are l 1628 parts per million of the sulphate in theresidue brine. Dividing that figure by thel known solubilities at thevarious temperatures, we arrive at the curve of Fig. 7. At 212 F. thebrine is 96% saturated; at 155 and 55 F. substantially 87% saturated;and le'ss saturated in the range between those last named temperatures,vwith a margin; and preferably at or near ythe upper end of thatrange-or, expressed otherwise, at a temperature just under (by anaccepted safety margin) the upper temperature at which the brine becomessaturated.

I have said that any suitable source of heat may be utilized. Generallyspeaking, the central heater or evaporator may be designed to utilizeany of the commonly known sources of heat, such as hot combustion gases,or electrical resistance. In Fig. 4 I show a modified form of structurein which a central heater indicated generally by the numeral 50 mayrepresent a heater of any type. for instance one intended to be heatedby combustion of fuel gas. I n this modication the heater 50 is shown asincluding or as being immediately surrounded by a heated tubular wall22a which, in effect becomes the member which presents the primarysurface at .which the raw water is first heated and vaporized and atwhich the majority of the vaporization takes place. A combustion chamber5I and burners 52 are shown, and a baille system 53 inside the tube 22ais designed to create a turbulence of ow or the hot combustion gases tocause maximum heat transfer to wall 22a. In this 'modified form the rawwater enters at I3a into the lower end of condenser coil I2a, leavingthe upper end of the condenser coil through the tube lla which carriesthe then heated water to the port or passage 15a which communicates withthe lower end of the annular space between heater wall 22a and anupstanding tubular shell 20a which is mounted at its lower endin thelower plate structure 24a.

, overflows and passes down over the surface of tube 20a and downthrough the annular space between that tube and the suspended bame tube32a, which corresponds to baille tube 32 in the structure rst described.The mixed iluids then flow downwardly in the annular space between 20aand 32a until the lower edge of 32a is reached, when the unvaporizedliquid, andthe air to some extent. are separated out, to be removed inthe same manner as described in connection with Figs. 1, 2 and 3, or tobe removed at the residue outlet Ila. The vapors. and the-remainder otthe air then pass upwardly between baille tube 32a and the upstan ingbaille tube a, and over the upper edge of alla into the annularcondensing -passage in 'which condensing coil Iza is located. Thecondensate is removed at 35a; and the iixed gases may be removed at thestandpipe. 38h, in the manner before described.

It will be noted that in both ofthe apparatus forms which I havedescribed, the mixed iiulds after leaving the evaporator move through adownward passage, inside the dependent baille 82 or 32a, and then havetheir now direction reversed to pass up, inside the upstanding bailletube SII or 3M, to nally ow downwardly through the surrounding condenserzone and over the condenser coils. This sam path ol dow, which greatlyfacilitates the separation of the residue liquid and the xed gases, ismaintained in both forms of heater, although in one of these forms theinithat shell. In the form of Fig. 4, the first downward pass of theduid is outside the upstanding tube 20a within which the uid rst flowsupwardly. Tube 213e is thus somewhat similar to the outer shell 2@ oi'the heating evaporator in Fig.l 1, particularly as some portion of theliquid may be vaporized in flowing down around it; but tube 2da needs noexternal insulating layer, as all of the heat which reaches it istransferred through the uid within it. The annular body of fluid betweena and 2tlg thus becomes in eilect the insulating layer for tubular shell20a over which the duid passes downwerdLv. And tubular wall 22a needs nospecial insulating layer, as thev fluids rise and ow upwardly around itvery turbulently ina more or less solid body which virtually precludesthe deposition of scale. At the point where the heated raw water entersthe space at the bottoni of tubular shell 22a a small bame or vane,indicated at du, may be installed for the purpose ci throwing theentering stream into tangential motion, so that the movement of theiuids upwardly through the simular space around 222e is at relativelyhigh velocity, swirling and turbulent. This increases the rate of heattransfer and also the uniformi-ty o heat transl-er.

The form or apparatus shown in Fig. l may be operated undercontrolledcondltions of temperature, pressure and volumetric liow, thesame es has been described for the forms of apparatus of Fig. l. Eitherform may be operated for multistage evaporation with two or more unitsin series. Operating in the manner which l have described, both forms of'the apparatus have a `very high thermal emciency. The gro'ss heat re-`quirexnent per pound of distilled water is only 1318 B. t. u. In factthe efficiency is so high that, with heat supplied from compressedbutane or propane, it is practicable to use my distillation unit inconvenient size to provide ample water for life boats. The compactnessand simplicity of the unit is also an important factor in any such use,and its construction makes possible its continued operation even whilebeing tossed about with the boat.

I claim: y 1. In distillation apparatus of the type which fi,sasf,ss. vI y includes a central verticallyextending evaporal tion heater, acondenser spacedly surrounding the heater, and structure includingpassages for introducing raw cool liquid to the condenser, for passingthe condenser liquid to the evaporation heater and for passing vaporsfrom the heater Ainto condensing contact with the condenser, to-

condenser, the outlet for unvaporized residue communicating with saidpassage at its lowermost point at its reverse turn.

2. Distillation apparatus as deiined in, claim 1, and in which thedownwardly extending passage yleading to the reverse turn is of ysmallercross-sectional area than the upwardly extending passage leading fromthe reverse turn, so that the vel locity of uid iiow into the reverseturn is relatively high as compared with the flow away from that turn.

3. Dlstillation apparatus as defined in claim 1,

lower edge, a member forming an annular pas-` sage bottom surroundingthe heater and spaced below the lower edge of said baille tube and fromwhich bottom the residue outlet leads, and another baille tube spacedlysurrounding the first mentioned baille tube, extending upwardly fromsaid bottom member and having a free upper edge over which vapors mayiiow to the condenser.

4. Distillation apparatus as deiined in claim 1, and in which thepassage forming structure comprises a depending baille tube spacedlysurrounding the evaporation heater and having a free lower edge, amember forming an' annular passage bottom surrounding the heater andspaced below the lower edge of said baille tube and from which bottomthe residue outlet leads, and another baiie tube spacedly surroundingthe rst mentioned baille tube, extending upwardly from said bottomm'ember and having a free upper edge over whichy vapors may flow to thecon-- denser, the annular passage formed between the first mentionedbaille tube and the heater having a smaller cross-sectional area thanthe annular passage formed between the two baille tubes. 5. Indistillation apparatus of the type which includes an outer verticallyextending shell, an annularly arranged condenser element within theshell, and a central evaporation heater within the condenser element andannularly spaced therefrom; the combination of means for passing raw.liquid through 4the condenser and thence upwardly through theevaporation heater, an inner tubular baille spacedly surrounding theheater, having a closed upper end and an open lower end and enclosing anannular passage for downward iiow of fluids around the heater, an outertubular baille spacedly surrounding the inner baille, and annularlyspaced inwardly from the condenser element, having an open upper end anda closed lower end which is spaced below the lower open end oi' theinner baille, said outer baille enclosing an annular passage throughwhich fluids travel upwardly after emergencefrom the open lower end ofthe inner baille, the open upper end oi' the outer baille communicatingwith the upper end of the annular space outside that baille and adjacentthe condenser element, a condensate outlet leading from the lower partof the annular space adjacent the condenser,` and a residue liquidoutlet leading from the lower part of the annular end of the annularspace adjacent the condenser.

A Ul

7. Distillation apparatus of the type deilned in claim 5, and includingan air outlet leading l from a point near but spaced above the low'erend of the annular space adjacent the condenser, the residue liquidoutlet `being provided with a trap and joined beyond its trap'with theair outlet.

8. In distillation apparatus of the type which includes an outervertically extending shell closed at top and bottom, an annularlyarranged condenserelement within the shell and close to its wall, and acentralevaporation heater within the condenser element and annularlyspaced therefrom; the combination of means'in association with theheater forming an upward heating passage for 1iquidan outer shell inassociation with the heater and over which uids iiow downwardly. fromthe upper end of the heating passage, means for introducing raw liquidto thev condenser and thence into the lower end of the heating passage,an inner tubular bafile annularly spaced around the heater shell andhaving 'a closed upper end and an open lower end and endenserelement. toform an annular passage for upward ow of iluids around the inner bame Afrom the lower end of the inner baille, and to form anannularcondensation passage adjacent the condenser element, the upper end ofthe outer haine being open and its lower end being closed at a levelbelow the lower open end of the between the inner and outer bailles, soas to cause relatively high velocity of downward iiuid flow in the iirstmentioned passage to the lower end of the inner baille.

13. In distillation apparatus of the type` which includes an outervertically extending shell closed at top and bottom, an. annularlyarranged con, denser element within the shell and close to itsv wall,and a central evaporation heater vwithin the condenser element' andannularly spaced therefrom; the combination which is characterized bythe central heater being of the fluid heated type and having an externalshell Vand a plurality of interior tubes forming an upward heatingpassage for liquid,means for introducing raw liquid to the condenser andthence into the lower end of the heating passage, an inner tubularbaille annularly spaced .around the heater shell and having a closedupper end and an open lower end and enclosing an annular passage fordownwardy flow of fluids around the heater shell, an outer tubularbaille spacedly surrounding the inner baille andannularly spacedinwardly from the condenser element, to form an annular passage forupward ilowof fluids around the inner baille from the lower end of theinner baille, and to form an annular condensation passage adjacent thecondenser element, the upper end ci the outer baille being open and itslower end being closed at a level below the lower open end of the Ainnerbaille, the open upper end of the outer baille communicating with theupper part of the condensation passage, a condensate outlet leading fromthe lower end of the condensation passage, a 'residue liquid outletleading from the lower end of the annular passage enclosed by j at topand bottom, an annularly arranged coninner baiiie,r rtlie open upper endof the outer baille communicating with the upper part of thecondensation passage, a condensate outlet leadl ing from the lower endof the condensation pas sage, a residue liquid outlet leading from thelower end or the annular passage enclosed by the outer baille at a pointbelow the open lower end of the inner baille, and an air outlet leadingfrom a point in the condensation passage near to but spaced above itslower end. Y

9. Distillation apparatus as defined in claim 5, and including a heatinsulating jacket around the exterior of the heater to retard theheating of fluids `flowing downwardly around the heater inside the innerbaille.

10. Distillation apparatus as dened in claim 8,:

and including a heat insulating jacket surround# ing the heater shell toretard the heating of uids flowing downwardly around that shell withinthe inner baille. Y

11. Distillation apparatus as defined in claim 5, and ingwhich theannular passage enclosed bythe inner baille around the heater is ofsmaller crosssectional area than the annular passage between the innerand outer baes, so as tocause relatively high velocity of downward .duidow in the first mentioned passage to the lower end of the inner bale.

12. Distillation apparatus as dened inclaim 8, and in which the annularpassage enclosed by the inner baille around the heater is o! smallercross-sectional area than the annular passage denser element within theshell and close toits wall, and a central evaporation heater within fthe condenser element and annularly spaced thence into the lower end ofthe heating pas-Q sage, an inner tubular baule depending from the closedupper end of the outer shell. said baule being annularly spaced aroundthe inner tubular shell and having an open lower end spaced above theclosed lower end of the outer shell, an outer tubular baule mounted atits lower end on the closed lower end of the outer shell. said outerbafile projecting upwardly in annular spaced re- Vlation around theinner baille and being annularly spaced within the condenser element and`having an open upper end, a condensate outlet leading from the lowerend of the space between the outer shell and the outer baie, a i'lxedgas outlet leading from the lower part of said last mentioned space, anda residue liquid outlet leading from the lower end of the annular spaceinsidethe outer baille.

I: I. 12.13A.

